302 cylinder problems

so i got my 302 running in my mustang and it was running very poorly, no power, and running rough.... so i decided to test by pulling plug wires off and found that when i pull 2,5,8 off that there was no change in idle.... so i checked to see if each of those plugs were sparking, sure enough they were.... so i pulled the valve covers, all my rockers were on right, except 1 on cylinder 7 had come off but that cylinder wasn't causing problems, so i fixed that... i cranked with valve covers off, sure enough all intake and exhaust valves were opening and closing.... so what could be causing 2,5,8 to not actually fire?

compression on all cylinders checks in at 120, spark plugs have a fat blue spark pushed out of a a petronix flamethrower coil and pertronix ignitor...

with a 120psi compression result you can safely assume there hasnt been any mechanical damage. are you sure fuel is getting to those cylinders? theres only three things needed for an engine to run. Spark, fuel/air mixture and compression. So, simply put, which one is missing?;)

the plugs look like they haven't made any contact with gas, but if my valves are opening, why wouldn't i be getting any fuel to 3 cyliners, ussually a carb or intake problem cuts off fuel to a whole bank

I do not know where u are at but where I am at,if anything sets for awhile u get critters in it ,up the exaust, down the carb, those places make nice homes to bug ,vermin and spiders!!!:LOL:

its an original ford intake manifold from 69, it was hot tanked and blasted about a year ago, and ran fine for 4000 miles, whole engine has about 4000 miles on it... i hardly doubt any critters crawled in though, i live in san diego... this problem just started happening after i pulled the engine out of my 69 galaxie and stuck it in my 66 mustang.... i'm starting to believe something went wrong in my heads, because the machine shop that did my heads was a wee bit shady, but only charged $70 to do both of them seeing that i supplied all the hardware...so i think I'm going to take them in to a much more reputable machine shop and have them take a look at my heads.... i'm just very unhappy about having to pull the intake manifold and heads.... i never like doing it...

well thanks for the tip, i actually got the same tip from john at JMC motorsports today, did a vac check and it was all over the meter, then i also notices a little oil buildup on the edges of the intake manifold, i decided i will have john do the manifold for me, he said he would charge me $20 to take it off, clean it up and reseal it, can hardly get gaskets for that price now anymore.... so i figured, why not... i'll let ya know tomarrow if i got all 8 cylinders again